Reinforced composites are used in a wide variety of applications. The best known composites are made from two-dimensional fabrics and/or fibers dispersed in a resin or plastic matrix. These composites are basically a resin or plastic structure to which reinforcing fabrics or fibers have been added to enhance the physical properties of the structure. The fabric or fibers have no self-supporting three-dimensional integrity. Nor do they provide significant, if any, interyarn friction along the three orthogonal axes.
These prior art reinforced materials have the serious drawback of lacking significant strength between one layer of fabric and its adjacent layers. Reinforcement effectively occurs in one plane only and is greatest within this plane in the directions parallel to the interwoven yarns. Little or no reinforcement is present in the direction perpendicular to the fabric plane.
Recent advances in the field of aerospace technology have created a need for high strength, temperature resistant materials that possess the necessary properties needed to protect re-entry vehicles from the severe thermomechanical stresses encountered within their re-entry environment. Existing carbon-carbon materials have proven somewhat effective as materials for nose tip application and show adequate thermal stress performance. Unfortunately, however, these materials are deficient in mechanical strength for some applications and have shown unpredicted anomalies in their ablation characteristics.
A wide range of reinforced, three-dimensional composite structures are now available. The simplest of these structures is the three-directional (3D) structure which has generally reinforcing elements which are mutually orthogonal. The most complex, which has been described, is a thirteen-directional (13D) structure. These thirteen directions, with reference to a cube, form three subgroups: the three edges, the four long diagonals, and the six diagonals of the faces.
Although the 3D structure is well balanced, compact and easy to fabricate, it does not generally provide the desired level of resistance to deflection and fracture due to shear deformation in bending. As the number of directions of reinforcement is increased, the resistance to shear compared with the 3D structure is improved, but the difficulty of fabrication of more complex structures increases greatly. Thus, what is desired is a structure which is relatively easy to fabricate and which exhibits desired mechanical properties.
Accordingly, it is a primary object of the present invention to provide an improved multidimensional composite structure.
Another object of the present invention is to provide a protective material for re-entry vehicle nose cones.
Yet another object of the present invention is to provide maneuvering re-entry vehicle nose tips having improved properties.
These and other objects and advantages of the present invention will become more readily apparent upon consideration of the following detailed description when taken in conjunction with the accompanying drawings.